Help-wrapper classes

[Praveen Seluka]

Hi all

I have been reading about wrapper classes.
I have a doubt.

Integer i=new Integer(2);line 1
Integer j=Integer.valueOf(2);line 2
Integer i=2;line 3

Line 1 - It creates a new Integer object
Line 2 - The method returns a newly created integer object
Line 3 - what does this line do.Object creation?

Help me in understanding this.

Thanks
Praveen Sp

[Pooja Jindal]

Yes, Line 3
Integer i=2 also creates a new Object.
But there is a difference between
Integer i=2 //Line 1
and Integer i=new Integer(2); //Line 2

How?
Here is an Example to Illustrate it:-

Integer i1 = new Integer(2);
Integer i2 = new Integer(2);
if(i1 != i2) System.out.println("different objects");

This would always Print "different objects" since new Object is created everytime you use new Keyword.

But if you do it like this,
Integer i1 = 2;
Integer i2 = 2;
if(i1 != i2) System.out.println("different objects");

Both i1 and i2 refers to same Object !.So it wont Print "different objects".


However it is subject to some conditions,
two instances of the
wrapper objects will refer to same Object when their primitive values are the same and each of these is :
Boolean
Byte
Character from \u0000 to \u007f (7f is 127 in decimal)
Short and Integer from -128 to 127

[Praveen Seluka]

hi pooja

why does this happen/

Integer i1=new Integer(2);
Integer i2=new Integer(2);
here (i1!=i2)
Integer i1=2;
Integer i2=2;
here (i1==i2)


If both types create Integer wrapper object,why is this strange behaviour.

Thanks
Praveen SP

[Jesper de Jong]

Originally posted by Praveen Seluka:
Integer i=2;line 3
Line 3 - what does this line do.Object creation?

An Integer object is created automatically by autoboxing.